Physocarpus plant named &#39;ZLEYe12&#39;

ABSTRACT

‘ZLEYel2’ is a new and distinct cultivar of Physocarpus opulifolius plant having an upright, mounded, dense plant habit; compact overall plant size; strong branching characteristics; small yellow-green foliage; short internode length; resistance to powdery mildew; corymbs of small blush-white flowers; coral pink to red follicle color in full sun for about a month after fertilization; and ability to root and grow vigorously from softwood and semi-hardwood cuttings.

Latin name of genus and species: Physocarpus opulifolius.

Variety denomination: ‘ZLEYel2’.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct cultivar ofPhysocarpus opulifolius and will be referred to hereafter by itscultivar name, ‘ZLEYel2’. Physocarpus opulifolius is a deciduous shrubgrown for landscape use. The key objective within the Physocarpusopulifolius breeding program I initiated in St. Paul, Minn. was todevelop new Physocarpus opulifolius cultivars that are compact growing,well-branched, healthy, and possess colorful foliage. One objective hasbeen to produce a cultivar with the yellow-green foliage color ofPhysocarpus opulifolius ‘Dart's Gold’ (not patented) and the compact,well-branched growth habit and small foliage of cultivated ninebark suchas Physocarpus opulifolius as var. nanus (not patented) or itsdescendant Physocarpus opulifolius ‘Donna May’ (disclosed in U.S. PlantPat. No. 22,634).

‘ZLEYel2’ originated by crossing Physocarpus opulifolius ‘Donna May’ asthe female parent and Physocarpus opulifolius ‘Dart's Gold’ as the maleparent. The pollination that led to the population of seedlings fromwhich ‘ZLEYel2’ was identified occurred in June 2011. The seeds of thispopulation germinated during the winter of 2011/2012 indoors underflorescent lights in St. Paul, Minn. Seedlings were grown in containersduring their first year. At the end of the first growing season,seedlings with attractive foliage color, relatively compact growthhabits, and powdery mildew resistance were retained. Selections wereplanted outside during their second growing season. ‘ZLEYel2’ wasrecognized as a highly desirable genotype among this seedling populationduring the summer of 2012. ‘ZLEYel2’ was planted outside in 2013 and wasfirst asexually propagated using semi-hardwood stem cuttings in thespring of 2013. I have found that the characteristics of ‘ZLEYel2’ arestable and true to type over successive generations of vegetativepropagation.

‘ZLEYel2’ was unique from the other ninebark seedlings because of itssmall yellow-green foliage and compact, very well-branched plant habit‘ZLEYel2’ first flowered in 2014 with attractive blush-white flowersthat are abundant and attractive against the yellow-green foliage. Asfollicles develop in full sun, they are a coral pink to red color forabout a month and provide additional ornamental value.

SUMMARY OF THE INVENTION

The primary objective of the breeding project was substantiallyachieved, along with other desirable improvements, as evidenced by thefollowing unique combination of characteristics that are outstanding inthe new variety and that distinguish it from its parents, as well asfrom all other varieties of Physocarpus opulifolius of which I am aware:

-   -   1. Upright, mounded, dense plant habit;    -   2. Compact overall plant size;    -   3. Strong branching characteristics;    -   4. Small yellow-green foliage;    -   5. Short internode length;    -   6. Resistance to powdery mildew;    -   7. Corymbs of small blush-white flowers;    -   8. Coral pink to red follicle color in full sun for about a        month after fertilization;    -   9. Ability to root and grow vigorously from softwood and        semi-hardwood stem cuttings.

Asexual reproduction of this new cultivar by rooting of softwood andsemi-hardwood cuttings, as performed at River Falls and Menomonie Falls,Wisc. and St. Paul, Minn. shows that the foregoing and all othercharacteristics and distinctions come true to form and are establishedand transmitted through succeeding asexual propagations.

Comparison With Parents

‘ZLEYel2’ has a similar overall plant size and dense, well branchedplant habit as its maternal parent ‘Donna May’. The branching of‘ZLEYel2’ is slightly more abundant within the plant canopy than ‘DonnaMay’ and leads to ‘ZLEYel2’ having a slightly more dense and slightlymore rounded overall plant silhouette than ‘Donna May’. Leaf size of‘ZLEYel2’ is similar to ‘Donna May’ with ‘ZLEYel2’ having slightly widerleaves. Internode length of ‘ZLEYel2’ is slightly shorter than ‘DonnaMay’. Inflorescence and flower size are similar between ‘Donna May’ and‘ZLEYel2’. ‘ZLEYel2’ differs most significantly from ‘Donna May’ in thatthe foliage color is yellow-green instead of purple.

‘ZLEYel2’ has a similar foliage and flower color to its paternal parent,‘Dart's Gold’. It differs from ‘Dart's Gold’ in that the leaves, stems,internode length, and flowers are all smaller for ‘ZLEYel2’. ‘ZLEYel2’is more dense and well-branched than ‘Dart's Gold’ and has an overallsmaller plant size than ‘Dart's Gold’. Follicle color of ‘ZLEYel2’ afterfertilization and as follicles swell is a more vibrant coral pink to redcolor and it holds the attractive follicle color longer than ‘Dart'sGold’.

Comparison of ‘ZLEYel2’ With Similar Cultivars

The Physocarpus opulifolius cultivar with the greatest similarity to‘ZLEYel2’ is Physocarpus opulifolius ‘SMNPOTWG’ (disclosed in U.S. PlantPat. No. 28,857). Young plants of ‘SMPOTWG’ were purchased as liners inquart-sized pots in spring 2017. Plants of similar size of ‘ZLEYel2’(propagated in 2016) were available and both cultivars were transplantedinto 2 gallon pots in spring 2017 and grown without pruning. As ofmid-summer 2017 plants of ‘ZLEYel2’ had more abundant branchingoriginating from axillary buds on current season stems and a much fullerand rounded plant form than ‘SMPOTWG’. Foliage size and color weresimilar between genotypes. A larger, flowering plant in a 2 gallon potof ‘SMPOTWG’ was purchased spring 2017 from a local garden center tocompare flowering and follicle color. The developing follicles on anolder flowering plant in the landscape of ‘ZLEYel2’ had a stronger coralpink to red coloration than the developing follicles on the potted plantof ‘SMPOTWG’. I have not had the opportunity yet to observe a maturespecimen of ‘SMPOTWG’ in a landscape to compare the mature plant sizewith ‘ZLEYel2’.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying colored photographs illustrate key features of‘ZLEYel2’. The photographed plant is in its sixth growing season in2017, the year the photographs were taken. Photographs show the colorsas true as it is reasonably possible to obtain with coloredreproductions of this type. Colors in the photographs may differslightly from the color values cited in the detailed botanicaldescription, which accurately describe the colors of ‘ZLEYel2’.

FIG. 1 illustrates a six-year-old plant of ‘ZLEYel2’ integrated in alandscape with other shrub species before flowering May 2017.

FIG. 2 illustrates a two-year-old plant of ‘ZLEYel2’ growing in anursery row in September 2017.

FIG. 3 illustrates corymbs of flowers of ‘ZLEYel2’ in mid-June 2017.

FIG. 4 illustrates a close up of flower buds and open flowers of‘ZLEYel2’ in mid-June 2017.

FIG. 5 illustrates developing follicles of ‘ZLEYel2’ in July 2017.

FIG. 6 illustrates stems at the base of a six-year-old plant of‘ZLEYel2’ displaying exfoliating bark November 2017.

DETAILED BOTANICAL DESCRIPTION

The following is a detailed description of ‘ZLEYel2’, the newPhysocarpus opulifolius cultivar, with color descriptions usingterminology in accordance with The Royal Horticultural Society (London)Colour Chart (2001), except where ordinary dictionary significance ofcolor is indicated. The phenotype of the new cultivar may vary withvariations in environmental, climatic, and cultural conditions, as ithas not been tested under all possible environmental conditions.Descriptions are based on observations of the original seedling duringits fifth year of growth in 2016 in River Falls, Wis. and two andthree-year-old plants propagated from semi-hardwood cuttings.

-   Classification:    -   -   Botanical.—Physocarpus opulifolius ‘ZLEYel2’.        -   Common name of species.—Physocarpus or ninebark.        -   Commercial.—Deciduous shrub.-   Parentage:    -   -   Seed parent.—Physocarpus opulifolius ‘Donna May’ (disclosed            in U.S. Plant Pat. No. 22,634).        -   Pollen parent.—Physocarpus opulifolius ‘Dart's Gold’ (not            patented).-   General description:    -   -   Plant habit.—Upright, mounded, and compact.        -   Plant size.—1.0-1.3 m in overall height and width.        -   Growth habit.—Vigorous and dense with abundant branching.        -   Blooming period.—About 21 days from mid-June to early July.        -   Hardiness.—Cold hardy to USDA Zone 3.        -   Root description.—Fibrous and vigorous.        -   Diseases and pest resistance.—‘ZLEYel2′ has shown strong            resistance to powdery mildew, even with other ninebarks            infected with powdery mildew growing adjacent to it. There            are multiple species of fungi that cause powdery mildew on            ninebark, and it is unclear which species of fungi were            infecting the adjacent, susceptible ninebark genotypes. No            other diseases or insect pests of ninebark have been            observed on ‘ZLEYel2’.        -   Cultural requirements.—‘ZLEY el2’ does well in full to            partial sun and well-drained, moderately fertile soil.-   Growth and propagation:    -   -   Propagation.—Softwood and semi-hardwood stem cuttings have            been effective.        -   Time required for root initiation and initial            development.—It takes about 3 to 4 weeks during the summer            using intermittent mist in the greenhouse without            supplemental lighting for cuttings to typically form visible            roots.        -   Time required to obtain a well-rooted cutting.—It takes            about 6 to 7 weeks to produce a well-rooted cutting in a 2            inch container.-   Branch description:    -   -   Branch color.—The color of current season stems is            Yellow-Green Group N144A. Sides of current season's stems in            full sun have reddish highlights closest to Red-Purple Group            58A due to the production of anthocyanin pigment. The most            mature stems on four-year-old plants had a mixture of colors            on the exfoliating bark; primarily Greyed-Orange Group 164A            and Greyed-Orange Group 165B, but there were also lighter            colored areas close to Greyed-Yellow Group 161A and darker            colored areas close to Greyed-Orange 165A.        -   Branch size.—Branches produced during the current season of            growth ranged from approximately 15 cm to 60 cm in length            and 1 to 4 mm in width. The oldest branches on four-year-old            plants were up to 2.0 cm in diameter at the base of the            plant.        -   Branch surface.—Young stems: Glabrous with a slight sheen.            Older stems: Exfoliating bark layers that are somewhat dull            and no longer have a sheen.        -   Internode length.—1.0 to 2.0 cm.        -   Branch habit.—Vigorous current season's stems tend to            produce new stems from axillary buds without pruning. This            leads to an abundantly branched and dense plant. The angle            between the new stems arising from axillary buds and the            stem from which they originated is typically 20-60°.-   Foliage description:    -   -   Overall leaf size.—Leaf length is typically about 3.5 cm and            leaf width is 1.5-1.75 cm.        -   Leaf division.—Simple.        -   Leaf attachment.—Petiolate.        -   Leaf arrangement.—Alternate.        -   Leaf number.—It varies, but an actively growing branch can            easily produce 30-60 leaves in a growing season.        -   Leaf blade shape.—Ovate in overall outline with three            prominent lobes.        -   Leaf blade base.—Rounded.        -   Leaf blade apex.—Acute.        -   Leaf blade venation.—Primary venation is palmate with three            principal veins. Each principal vein diverges at the            juncture of the leaf blade and petiole and travels through            the middle of one of the three lobes. Secondary venation off            of the three principal veins is pinnate.        -   Leaf blade margin.—The three primarily lobes have secondary            undulations or lobes. The margin on the three primary lobes            is best described as doubly serrate.        -   Leaf blade surface.—Glabrous on upper and lower surfaces.        -   Leaf blade size.—The leaf blade is approximately 2.5-2.75 cm            long and 1.5-1.75 cm wide.        -   Leaf blade color.—Young emerging leaf blades are            Yellow-Green Group 153D on the upper and lower surfaces.            Young expanded leaf blades are closest to Yellow-Green Group            N144A on the upper surface and Yellow-Green Group 146D on            the lower surface. Mature leaves are Green Group 137C on the            upper surface and Yellow-Green Group 146C on the lower            surface.        -   Petiole size.—About 1.0 cm in length and about 1 mm in            width.        -   Petiole shape.—Sulcate. The petiole is generally round            except for a longitudinal furrow running the length of the            upper surface.        -   Petiole color.—Yellow-Green Group 146D.        -   Petiole texture.—Glabrous.        -   Stipule number.—There are two stipules at each node with one            on each side of the leaf petiole where it attaches to the            stem.        -   Stipule size.—2-3 mm long and 1.25 mm wide.        -   Stipule shape.—Generally lanceolate.        -   Stipule color.—Yellow-Green Group 146D.-   Flower description:    -   -   Inflorescence type.—A corymb with 18-25 rotate flowers            arranged in a hemisphere.        -   Inflorescence size.—Typically 1.5-2.0 cm in height and            width.        -   Inflorescence lastingness.—The corymb has open flowers            typically for up to 21 days with each individual flower open            for approximately 3 days.        -   Flower bud shape.—Elliptic to oval.        -   Flower bud size and proportions.—2.5-3.0 mm in length and            2.0 mm in width. The receptacle of the bud accounts for            about one half of the proximal end and the calyx accounts            for about a half of the distal end of an unopened flower            bud.        -   Flower bud color.—The overall color of exposed petal            undersides as the sepals open can best be described as White            Group 155B. In bright light, there are highlights of            Orange-Red Group N34C. The sepals and receptacle are closest            to Yellow-Green Group 146C.        -   Flower size when fully open.—4.5-5.5 mm in diameter and 4.0            mm in depth (not including pedicel).        -   Flower fragrance.—Slight and sweet.        -   Petal number.—5.        -   Petal size.—2.0-2.5 mm in length and width.        -   Petal shape.—Elliptic to obovate.        -   Petal color.—Expanding petals are White Group 155B on the            upper surface and White Group 155B on the lower surface. The            highlights of Orange-Red Group N34C on the petals as the            flower buds just start to open are typically no longer            present when the petals are fully expanded.        -   Sepal number.—5.        -   Sepal size.—Length is 2.0-3.0 mm and width is 1.0-1.5 mm.        -   Sepal shape.—Deltoid.        -   Sepal color.—Yellow-Green Group 146C.        -   Pedicel size.—The length ranges from about 1.5 cm for the            flowers around the perimeter of the corymb to about 0.7 cm            for the flowers nearest the terminal or center of the            corymb. All pedicels are about 1.0 mm in diameter.        -   Pedicel color.—Yellow-Green Group 146C.        -   Subtending bract size.—There is a subtending bract where            each pedicel meets the peduncle of the corymb. The            subtending bract is 2.0-3.0 mm long and 1 mm wide below the            pedicels at the proximal end of the corymb to 1.0-1.25 mm            long and 0.75-1.0 mm wide for the more distal pedicels at            the terminal of the corymb.        -   Subtending bract shape.—Elliptic to obovate.        -   Subtending bract color.—Yellow-Green Group 146C.-   Gynoecium:    -   -   Pistil number per flower.—Typically there are 4, but            sometimes 3.        -   Stigma shape.—Globular.        -   Stigma size.—0.25 mm in diameter.        -   Stigma color.—Yellow Green Group 146D.        -   Style shape.—Linear.        -   Style size.—About 4 mm long and 0.2 mm wide.        -   Style color.—Yellow Group 145D.        -   Ovary shape.—Elliptic.        -   Ovary size.—About 0.4 mm in length and 0.3 mm in width.        -   Ovary color.—Yellow Green Group 146C.-   Androecium:    -   -   Stamen number per flower.—Approximately 25.        -   Anther shape.—Elliptic to round.        -   Anther size.—0.5 mm in height and width.        -   Anther color.—Red Group 53A.        -   Pollen color.—White Group 155C.        -   Pollen abundance.—Moderate.        -   Filament shape.—Linear.        -   Filament size.—1.0-3.0 mm long and 0.1-0.2 mm wide.        -   Filament color.—Yellow Group 145D.-   Fruit and seeds:    -   -   Fruit.—There are typically three or four firm-walled            follicles that form per flower. Follicles can split along            both sides of the seam, but split more readily along the            inner or adaxial seam. Follicles are elongated and generally            ovate in shape with acuminate tips. They are up to 8.0 mm            long and approximately 2.0 mm wide. After fertilization and            expansion of successfully developing fruit, the surface has            a rich vivid coral pink to red color in bright light close            to Red-Purple Group N57B. Follicle color tends to be green            when out of direct sunlight and near Yellow-Green Group            145D. As the follicles continue to mature the red coloration            dissipates. When mature and before turning brown the color            is Greyed-Yellow Group 161A. The final color when follicles            open and release their seeds is Brown Group 200C.        -   Seeds per follicle.—There are up to 2 seeds per follicle.        -   Seed shape.—Ovate.        -   Seed size.—Up to about 1.75 mm long and 1.25 mm wide.        -   Seed color.—Mature seed color as follicles open and seeds            are exposed is closest to Greyed-Orange Group 164A.-   Cytology:    -   -   Ploidy.—Diploid (2n=2x=18). Meristematic root tip cells in            the stage of metaphase of mitosis were observed to have 18            chromosomes under a compound microscope at 400x            magnification.-   Winter hardiness: Acclimated plants of ‘ZLEYel2’ have displayed    strong stem survival (complete survival to minor tip dieback) in    United States Department of Agriculture cold hardiness zone 3 and    warmer without insulation.

I claim:
 1. A new and distinct cultivar of Physocarpus opulifolius plantsubstantially as herein shown and described, characterized particularlyby its upright, mounded, dense plant habit; compact overall plant size;strong branching characteristics; small yellow-green foliage; shortinternode length; resistance to powdery mildew; corymbs of smallblush-white flowers; coral pink to red follicle color in full sun forabout a month after fertilization; and ability to root and growvigorously from softwood and semi-hardwood cuttings.